Note: Descriptions are shown in the official language in which they were submitted.
MP1289-CA
Related Applications
This application is a con~inuation-in-part application of
U.S. Application Serial No. 07/246,399 filed September 19,
1988 and completely incorporated herein by reference for all
purposes.
Field_of the Invention
This invention relates to an electrical connection device
providing strain relief integrally but apart from the point of
electrical contact. More specifically, this invention relates
to an electrical connector preferably in a terminal block. In
particular, this invention relates to a rotary or push
electrical connector for terminal blocks described in U.S.
applications serial No.s 07/070,475 filed July 7, 1987,
entitled "Terminal Block", now abandoned; 07/102,072 filed
September 29, 1987, entitled "Terminal Block Adapter", now
abandoned; 07/130,347 filed December 8, 1987, entitled
"Terminal Block Adapter", now abandoned; 07/157,442 filed
February 17, 1988, entitled "Telecommunications Terminal
Block"; 07/164,261 filed March 4, lg88, entitled
"Telecommunications Terminal Block or Adapter"; 07/164,301
filed March 4, 1988, entitled "Telecommunications Terminal
Block and Caps Therefor~; and 07/231,755 filed ~ugust 12, 1988,
entitled "Telecommunications Terminal Block or Adapter". Each
of the preceding applications is completely incorporated
herein by reference for all purposes.
Back~round of the Invention
Various configurations of terminal blocks are used in
the telecommunications industries or other industries which
require many wire connections at a terminal block, fuse box,
and the like in an apparatus. For example, the drop wire in
the telecommunication industry will be attached to a ter-
minal block such that the major cable will provide indivi-
MP1289 CA
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dual wires for the wires going to individual homes. Thefuse panel in homes or in machines often require many wire
electrical connections at a given point. When the electri-
cal and mechanical connection is made at the same point on
the wire to provide both the electrical connection as well
as mechanically holding the wire in place, the pivot point
of the mechanical connection may break the wire or the wire
may undergo a cold working at the attachment point which
over time results in a broken elec~rical connection. Eigh
vibration environments accelerate this situation and shorten
the connection's lifetime.
The Applications enumerated above teach innovative ter-
minal blocks and methods for forming electrical connections
without the need for wire stripping and bending around a
terminal post. This provides for a faster and stronger
electrical connection. Forming the electrical connection
without stripping the wire speeds the installation process
as well as provides additional protection for the wire for
strain relief purposes. This type of electrical connection,
although ideally suited for terminal blocks, finds applica-
tions in any device where it desirable to provide an electri-
cal connection while maintaining the vast majority of the
insulation on the wire apart from the point of the electri-
cal connection. Although this connection provides greater
strain relief than a stripped wire, a contact configuration
with greater strain relief would further increase the con-
nection lifetime and be highly desirable.
Specific applications such as Telecommunication's Terminal
Blocks often require forming electrical connections to a wide
variety of wire gauges. In the process of designing terminal
blocks for such wide variety of wire gauges, e.g., 24 gauge
through 18 1/2 gauge, the sizing of the block must be made to
accommodate the largest gauge wire, i.e., 18 1/2 gauge.
MP1289-CA
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However, in accommodating such a large gauge of wire, it is
often difficult to tell when the larg~ gauge wire can be
easily withdrawn from the terminal block without stripping the
insulation from the end of the wire. Stripping the insulation
from the end of the wire results in a time consuming process
to extract the insulation before a wire can be re-inserted.
The terminal block is also configured to tighten down on a
much smaller wire such as a 24 gauge wire. In providing for a
good electrical contact to the smallest wires, it is often
difficult to kDow when a good electrical contact is made to
the largest gauge wire with overtighteningO Thus, the
installer often overtightens the cap. This results in damage
to the cutting edge. It would be highly desirable to have a
terminal block configured to indicate when the largest gauge
wire can be safety withdrawn without stripping the insulation
while also minimizing or eliminating destructive over-
tightening on the large gauge wire. A still further desirable
feature would be a method and a means for providing feedback
on the positioD of the connection cap when tightening down to
the smallest gauge wire. Although an individual operation is
not time consuming. When working the many repetitions of the
process in a 50-terminal block results in greater and more
effective utilization of the craftsperson.
It is thus an object of this invention to provide an
electrical connection device which can electrically connect
a wire to a suitable terminal post or any electrical connec~
tion where enhanced strain relief benefits the reliability
of the connection. It is also an object of this invention
to form an electrical connection without the need for wire
stripping. A still further object of the invention provides
for an indication of when the large gauge wires can be
withdrawn from the terminal block without stripping insulation
therefrom while also avoiding overtightening upon installation
of the larger gauge wire. Additional objects of the invention
will be apparent from the following description.
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MP1289-CA
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Summary of the Invention
This invention provides an electrical connection device,
especiall~ suitable in terminal block applications, which
accomplishes the previously recited objects and obtains the
desirable features recited previously and also provides
additional benefits readily apparent to the skilled artisan
from the following more detailed description.
More specifically, the invention provides a device which
decouples the electrical connection portion of the device
from that portion which provides mechanical gripping of the
wire but retains these functions in an integral unitO Thus,
the portion of the wire subject ~o the need for strain
relief is held in place and surrounded by the buffering
insulation. This is accomplished by shaping the electrical
connector and base support to securely hold the wire iso-
lated from but in the same proximity as the electrical con-
nection being made by the cutting edge of ~he electrical
connector.
Additional embodiments of the invention provide for a
method and means of indicating when a larger gauge wire is
sufficiently disconnected from the base member to provide for
easy removal while also providing a method and means upon
installation for indicating when an electrical connection is
formed to the larger gauge wire without overtightening.
Brief Description of the ~rawings
-
Fig. 1 is a cross-sectional illustration of a single
sided terminal block for small gauge wire which incorporates
the concepts of the invention.
Fig. 2 is an exploded view of the cap and block portion
of the terminal block depicting the formation of an electri-
2~
- MP1289-CA
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cal contact with the wire and the mechanical gripping of the
wire to provide strain relief.
Fig. 3 is a cross-sectional illustrative view of a piece
of wire.
Fig. 4 illustrates a terminal block for a plurality of
wires.
Fig. 5 illustrates an embodiment for multiple wires.
Fig. 6 illustrates a connect/disconnect embodiment of the
invention for larger gauge wire.
Detailed Description of the Invention
The invention will be more paLticularly described with
reference to the Figures.
Fig. 1 represents a cross-sectional view of a terminal
block lO0. The terminal block 100 comprises a base member
lO and a cap 30. Base member 10 includes a first aperture
l~ capable of receiving the wire to which electrical contact
will be made and a second aperture 14 in communication with
the aperture 12 to receive the cap 30.
The base member lO further includes a conductive binding
post 16 fixed in the base member 10. The conductive binding
post 16 has a broader base region 18 and a portion 20 for
connecting to a conductive core 204 of a wire 200. The wire
200 has insulation 202 and the conductive inner core 204.
The conductive binding post 16 further includes a binding
post shoulder 22 broader than the threaded binding post sec-
tions 26 and 28. Between the binding post shoulder 22 and
above the broader base region 18 is binding post aperture 31
for receiving a drop wire 300 (Fig. 2). A drop wire 300 is
inserted through the first aperture 12 and pushed through
MP1289-CA
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the aperture 31 in t~e binding post 16 until it abuts the
portion of the base member 10 opposite to the aperture 12.
If the binding post aperture 31 includes a central divider
and the base member 10 includes an aperture opposite the
first aperture 12, Fig. 5, then the cap 30 can connect two
wires, pushed through the apertures to meet at the divider,
together. In a like fashion, a plurality of apertures in
the base member 10 and the binding post 16 permit a plura-
lity of wires to be connected.
The cap 30 includes an insulating outer part 32 and a
conductive inner part 34. The conductive inner part 34 con-
tains a threaded portion 36 to engage the threaded binding
post sections 26 and 28. The two threaded binding post sec-
tions 26 and 28 permit the cap 30 to be screwed down through
and unscrewed from the aperture 14 from the aperture 12
region without falling out of the terminal block 100. Only
if the cap 30 is further twisted to engage the threaded sec-
tion 28 can it be completely removed. This feature avoids
inadvertent loss of the caps 30. The cap 30 also includes a
mechanical contact/cutting edge 40 capable of cutting
through the insulation of the wire inserted through the
aperture 12. ~he mechanical contact/cutting edge 40, the
binding post shoulder 22 and the cap shoulder 38 are propor-
tioned so that when the cap 30 is completely tightened on
the binding post 16, there is sufficient space between
cutting edge 40a/40c and the broader base region 1~ so as to
not sever the smallest size of wire to be utilized with the
connector 100.
The electrical connection mechanical strain relief
feature is more specifically illustrated in Fig. 2. Fig. 2
is a blown up cross-sectional view of the portion of the
terminal block 100 with cap 30 in its tightened pocition on
a small drop wire. When tightened down onto a wire 300, the
MP1289-CA
cutting edge portion 40a cuts through and displaces the
insulation 302 to make electrical contact with the conduc-
tive core 304. A blunt chamfer 40b pinches the wire 300
for a tight mechanical hold with the base member 10 at the
base member edge 42. The blunt chamfer 40b can have any
shape, such as convex, concave, semi-circular, and the like
provided the surface pressures and deforms the wire 300
without completely severing the insulation 302. As
illustrated, sufficient space is allowed between 40a and the
base member 18 when the cap 30 is fully tightened so that a
positive electrical contact is made without completely
severing the conductor core 304 of the wire 300. Optionally,
edge 42 can also be chamfered or filled with the base member
material.
An additional optional feature is also illustrated in
Fig. 2. The positioning of the broadened base 18 is
recessed, as illustrated by region 44 to be slightly below
the aperture 12 and the binding post opening 31. When the
cap 30 is tightened, the wire 300 is crimped down slightly~
to ensure an additional and more positive electrical con-
tact at the edge 40c and the wire 302.
The gap between the cutting edge 40a and the broadened
base portion 18 is preferable a~ least equal to or less than
A plus Bl, or B~ hut sufficiently large to preclude cutting
the conductor core 304 or more preferably as illustrated in
Fig. 3. Of course, allowance must be made for the
compression of the insulation 302 under pressure. This
ensures an electrical contact to the conductive wire core
304. This distance is provided by proportioning the binding
post shoulder 2~ to meet the cap shoulder 38 with a length
for the mechanical contact/cutting edge 40 at the cutting
edge 4Oa to base 18 to be less than or equal to A plus Bl,
or B2 for the smallest size of wire utilized with the
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MP1289-CA
electrical contact device 100. Larger sizes of all copper
wire can be cut up to about fifty percent of the diameter A
and the strain relief feature ~nsures that any cold working
of the wire is away from the electrical contact portion.
The mechanical retention occurs between the blunt edge
40b and the base edge section 42. Preferably, the base 10
but especially the base edge 42 material yields before the
conductor wire 304. This prevents the edge 42 from cracking
or cutting the wire 304 and thus creating a weak point.
Thus the electrical contact function is decoupled from the
mechanical contact function. Of course, the pressure of
edge 40a on the wire 304 and broadened base 18 also provides
a means for retaining the wire. However, the additional
decoupled contact point through the wire 304 and insulation
302 of Bl, plus B2 provides mechanical retention less sub-
ject to cold working, i.e., this provides strain relief
apart from the formation of the electrical contact.
Optionally, the edge 42 can be shaped, i.e., chamfered to be
parallel with the edge 40b. When tightened, the distance
between 40b and 42 must be less than the diameter of the
wire 304 plus insulation 302, i.e., less than A+~l+B2. The
exact amount is a function the gripping power requried for a
particular application. In telecommunication applications,
the contact strain relief feature is most desirable for
small wires, i.e., 22 and/or 24 AWG, because larger wires,
i.e., 18 1/2 and/or 19 gauge, especially those with steel
core and copper claddings, provide sufficient mechanical
strength to be less subject to premature failure from fibra-
tion or cold workinq.
More specifically, strain relief is provided between the
edge 40b which pinches the insulation 302 to the shoulder
42. This provides the mechanical retention for the wire 300
in terminal block 100 apart from electrical contact and
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MP1289-CA
_g _
retention between 40a/40c and 18. Thus, the mechancial
retention means between 42 and 40b are isolated from the
primary electrical connection means 40a, 40c and 18. This
decoupled but integral mechanical retention and the adjacent
electrical contact provides strain relief for any electrical
wire subject to vibration or repeated twisting and pulling
without the need for additional wire restrainers, Thus, the
benefits of the terminal block designs described and
illustrated in the previously recited applications are main-
tained and enhanced with this additional strain relie~
feature.
Fig. 4 illustrates a terminal block 500 having a base
510 (10 in Fig. 1) with a plurality of apertures 512
(12 in Fig. 1) and a plurality of caps 530 (30 in Fig. 1)
fitted into a plurality of second apertures not visible. Of
course the other internal aspects of the invention, not
illustrated, are similar to the illustrations in Fig.s' 1
and 2. Fig. 5 illustrates the embodiment where a third
aperture 12a is opposlte the first aperture 12 and the con-
ductive binding post 16 contains a di~ider 45 for the abut-
ment of a wire inserted through the third aperture 12a. The
numbering of the similar items in Fig. 5 to Fig. 1 is
retained to simplify the understanding. The addition of
additional apertures, not illustrated, permit the coupling
of any desired number of wires. Furthermore, adjusting the
height of aperture base position of the aperture 12 as
illustrated by edge 42 in Fig. 2 and the base member 18,
permits coupling wires of different sizes. Additionally,
any voids in the terminal block can be sealed with a sealing
material such as a gel to provide environmental sealing. A
suitable gel has a cone penetration value as measured
according to ASTM D127-68 at 21C of about 100-350 (10~1 mm)
and an ultimate elongation as measured by ASTM D638-80 at
21C of at least about 200~. Greater details are specified
~ 3 MP1289-CA
in the previously recited applications. of course~ an open
or closed vented area wi~hin the base member 10 is preferred
when a gel is used in conjunction with the terminal block.
Fig 6 illustrates the connect/disconn~ct em~odiment of
the invention in a dual terminal block 600. Fig 6 is a
cross-sectional view of the terminal block 610 with the
exception that the cap 630 is illustrated in full to provide
an illustration of the connect/disconnect system. Those
features, which are similar to the features in Figs 1, 2,
and 5, have similar last two digits but start with the
hundreds digit of 6. More specifically, the cut-away view
of terminal block 610 contains binding posts 620a and 620b.
The base wires 800a and 800b have insulation 802a and 802b
with conductive cores 804a and 804b, respectively. The
wires are electrically connected to the binding posts 620a
and 620b, respectively. A large gauge wire, e.g., 18 1/2
gauge, 700 i5 electrically connected in section b of block
610.
The block 610 has first aperatures 612a and 612b. The
caps 630a and 630b are in the cap aperatures and threaded by
engaged to the binding posts 620a and 620b, respectively as
illustrated in Fig 1. The electrical/mechanical contact
cutting edges~are 640a and 640b, respectively. The connect/
disconnect apparatus provides an indicator system such as a
white line, raised marks, depressions, and the like with a
lower edge 650a which indicates when the cap 630 is suf-
ficiently withdrawn from the terminal block 610, as
illustrated by cap 630a, to avoid the jamming of the wire
700 within the block 610. Jamming the wire 700 can result
in stripping the insulation from the wire if it is pulled
while only partially disconnected. When the cap 630 is
tightened down, as illustrated in 630b, the top portion of
the indicator 660b illustrates when the cap has been suf-
~ MP1289-CA
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ficiently tightened down to form a good electrical contact
to the largest gauge wire, e.g.~ 18 l/2 gauge, without over
tightening or damaging the cutting edge 640b. The top indi-
cator 660b gives a feedback to the craftsperson when the
wire is sufficiently tightened down much in the same way as
tne bottoming out of ~he cap on the shoulder post of the
binding post when tightening down on a smaller gauge, i.e.,
a 24 gauge wire without severing it. Optionally, an addi-
tional indicator above 660a or 660b can be provided on the
caps 630a and 6~0b, respectively, to indicate the
approaching of the bottoming out of the cap on the binding
post to prevent the needless waste time by the operator in
tightening down on the smallest gauge wire.
Although the invention has been described with reference
to a terminal block for the telecommunications industies, it
would be readily apparent to the ordinary skilled artisan
that this mechanical/electrical contact and strain relief is
suitable for any type of electrical connection where strain
relief of the wire is necessary to avoid cold working and
premature failure. Modifications which would be obvious to
the ordinary skilled artisan are contemplated to be within
the scope of the invention for e~ample the cap 30 could
have male threads protruding from within the cutting edge 40
and screw into a female base. Furthermore, the cap and post
16 can be configured to engage in a racheting manner or by a
pressure fit rather than by screwing together. clearly the
cutting edge strain relief can be slotted rather than cir-
cumferential because only the leading edge provides the
strain relief feature in conjunction with the electrical
contact unless ~ultiple wires are connected through multiple
apertures. Thus the invention in its broadest concept is
the decoupling but integral connection of the electrical
connection point and the mechanical attachment point to
obtain a substantially single functioning unit. Any means
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MP1289-CA
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suitable for accomplishing this feature is contemplated to
be within the scope of the invention. Furthermore, any
indicator system such as dots or dashed lines on the cap as
opposed to a painted or marked band(s) is within the scope
of the connect/disconnect embodiment.
